Abstract
A metallic-nanoshelled rectangular dielectric rod is proposed to flexibly enhance and tune the structural absorption. Due to the ultra-small thickness of the metallic-nanoshells, electromagnetic (EM) waves can penetrate into the rods and rectangular cavity resonances can be formed. At the cavity resonances, the strong EM wave–matter interaction results in an enhancement in the structural absorption by more than one order of magnitude. By stacking the nanoshelled rods, a three-dimensional (3D) woodpile photonic crystal with both the rectangular cavity resonance and the photonic band gap effect is realized. As a result, the structural absorption of the nanoshelled 3D photonic crystal is significantly enhanced to ∼99.99% at the resonant wavelength.
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GENERAL SCIENTIFIC SUMMARY Introduction and background. Most of the unique features of metallic nanostructures are induced by either collective plasmonic effects or optical cavity resonances. For example, metallic spherical nanoshells have been investigated substantially because of their strong absorption caused by localized plasmon modes. Additionally, by utilizing optical cavity modes, field enhancement of a large volume and strong structural absorption have been realized in large-scale nanoshells and three-dimensional (3D) metallic photonic crystals. However, the absorption enhancement or tunability is less appealing, and the structures are difficult to integrate into solid-state nano-devices.
Main results. In this work, we propose to enhance and tune structural absorption by employing a rectangular cavity resonance in a nanoshelled rod (NRod), which consists of a dielectric rectangular rod coated with a gold nanoshell. The proposed NRods facilitate the resonances of higher-order cavity modes and the peak absorption can be enhanced by more than one order of magnitude. Moreover, by integrating the NRods into a 3D photonic crystal, structural absorption at the resonant wavelength is further enhanced to ~99.99 per cent.
Wider implications. The investigated absorption enhancement and tunability, as well as the higher-order mode excitation, make it possible to explore NRods as a candidature for potential photonic devices such as nanoscale sensors, efficient radiation sources and solar cell systems.
Figure. (a) Schematic of a one 1D film, 2D NRods and a 3D nanoshelled photonic crystal (NPC). (b) Calculated absorption spectra of the structures shown in (a).